After stoichiometric thick films were deposited on -cut substrates using the sol-gel method from a precursor solution containing various polyvinyl alcohol (PVA) concentrations, their characteristics were investigated. The film thickness increased linearly with the increase in PVA and precursor concentrations. The orientation relationships between films and substrates were determined by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, and the results showed that (006) oriented epitaxial layers with parallel epitaxial relationships could be grown on a -cut substrate. The refractive indexes of the films were and at a wavelength of , and their transmission loss was .

Dielectric spectroscopy and ultrasonic sound velocity were investigated for tetragonal single crystals over a wide range of temperature. In addition to the expected phase transition from the tetragonal ferroelectric phase to the cubic paraelectric phase at a high temperature, an abnormal ferroelectric phase transition below room temperature is observed. The low-temperaturephase transition shows a relaxor behavior though tetragonal single crystal is considered to be typical normal ferroelectrics. By comparing the dielectric constants of poled and depoled conditions and by analyzing oxygen-octahedra units of perovskite structure, it is suggested that the low-temperaturephase transition in poled tetragonal single crystal could be tetragonal to rhombohedral ferroelectric phase transition.

The heterostructure has been fabricated by pulsed-laser deposition on (001) single crystal substrate. The crystallization and surface morphology of the heterostructure have been characterized by x-ray diffraction and atomic force microscopy. The composition distribution along the depth of the heterostructure is analyzed by Auger electron spectroscopy. It is founded that the LSMO bottom layer shows a marked effect on the dielectric properties of the BST films. Comparing with BST∕YBCO (YBCO—) heterostructure grown by similar process, the dielectric loss exhibits much lower and less frequency dispersive, especially in the high frequency region. The loss tangent at is about 0.012 and the figure of merit factor is about 25 under the condition of . Ferroelectric hysteresis measurement shows that the remanent polarization and coercive field of the heterostructure are and , respectively. These parameters are all better than BST∕YBCO heterostructure. The good surface morphology and the element diffusion between BST and LSMO layers may be suggested to be responsible for the above-improved parameters of BST∕LSMO heterostructure.

We report on electric-field poling of (MgLN) using patterned electrodes. Investigation of electric properties of MgLN reveals that polarization switching causes reversible resistance change and that this phenomenon can explain the physical mechanism of random domain growth. Based on these results, we propose a domain-control method in MgLN single crystals by suppressing resistance reduction during the poling process. Using this method, short periodic structures consisting of submicron domain geometries have been achieved in -, -, and -cut MgLN crystals. High performances of these periodic domain-inverted structures are also demonstrated by evaluating their potentials as second-harmonic generation devices.

The far-infrared reflectivity spectroscopy with a normal and oblique (45°) light incidence has been performed with the spectra of (CCTO/SRO) and (CCTO/LSCO) heterostructures in the frequency range with a view to study the electronic and phonon properties of the high-dielectric CCTO thin films grown on the SRO and LSCO electrodes by pulsed laser deposition. The frequency dependence of optical conductivity, dielectric, and energy-loss functions of the CCTO films have been calculated by the Kramers-Kronig transformation. Analysis of the optical functions yields two different trends for two compositions, for CCTO/SRO, the electronic behavior is semiconductorlike (carrier concentration is in the order of , optical mass , free-carrier relaxation time ) and can be described by applying the Drude-Lorentz model on a plasma of free carriers, whereas for the CCTO/LSCO composition, Lorentz alone oscillator is enough to simulate the electronic part of the conductivity, revealing the presence of bound optically active electrons. We report also on the observation of additional longitudinal phonons at 756, 732, and by reflectivity measurements with an oblique beam incidence on CCTO/SRO. The phonons are assigned to Berreman modes. The CCTO/LSCO did not reveal longitudinal phonon modes. Based on the optical spectroscopy results and dc resistivity measurements, we can infer that the CCTO filmsdeposited on a SRO electrode consist of semiconducting grains which are influenced by deposition processing and substrate material.

We present a Raman spectroscopy study of the lattice-dynamical properties of the thin films with , 0.1, 0.2, 0.35, and 0.5 in the temperature range of . Soft phonon modes were observed, and the temperature dependence of their frequencies and Raman intensities were investigated. The Raman spectra of the films are compared with the single crystals of the same compositions. The essential differences in the lattice-dynamical properties of the thin films and single crystals are observed, such as the forbidden first-order Raman scattering in the films well above the phase-transition temperature in bulk, hardening of the soft phonon modes in films compared to crystals, and significantly larger range of the soft-mode overdamping in the films. On the other hand, the lattice-dynamics behavior in the films is found similar to that of the relaxor ferroelectrics. Analogous to the relaxors, the presence of the polar nanoregions existing in the films at the temperatures above the bulk ferroelectric phase transition explains the specific lattice-dynamical properties of the thin films.

Investigations of the structure-property relationships in . have been performed for between 0 and 0.08 by means of x-ray diffraction, electron microscopy, polarization, and dielectric studies. Factors affecting the phase stability were determined. The base composition was ferroelectric (FE) at room temperature and transformed into an incommensurate antiferroelectric state on heating. Evidence was presented that low La addition could destabilize the FE state and became at room temperature, which transformed to a multicell cubic state and then to a paraelectric (PE) phase upon heating. Further increase of La content enhanced the stability of the state at room temperature. Moreover, addition of La could also broaden the phase transition temperature region and decrease its maximal dielectric constant .

In this investigation, crystalline solutions have been fabricated by using the solid-state reaction method. A ferroelectric rhombohedral/tetragonal morphotropic phase boundary (MPB) of was observed for . In the vicinity of MPB, 0.6BLGF-0.4PBT revealed the maximum dielectric constant and piezoelectric constant of 1168 and , respectively. The substitution of Ba for Pb dramatically increased and of relative to at the same content. The Curie temperature of was determined to be above through the compositions investigated. The phase diagram of revealed a V-shaped relationship between and content. The planar coupling coefficient was measured to be 0.37 for 0.6BLGF-0.4PBT, which was stable with increasing the measurement temperature until . It is demonstrated that BLGF-PBT is a competitive alternative piezoelectric material, with the superior piezoelectricity and lead-reduced composition.

The phenomenon of polarization imprint consisting of the development of a preferential polarization state in ferroelectricfilms is known as one of the major issues impacting the development of high density ferroelectric memories. According to the commonly accepted scenario, the imprint is related to the charge injection and charge accumulation in the nearby-electrode passive layer of the ferroelectricfilm. Recent studies demonstrated that the coercive voltage shift induced by the imprint exhibits a nonlinear time dependence in a logarithmic scale. This result was interpreted as the presence of two different imprint mechanisms characterized by different activation energies. In the present work, an analytical theory of the injection scenario of imprint is developed. The charge accumulation at the interface is shown to provoke a voltage offset and polarization loss which are nonlinearly dependent on the time in logarithmic scale. This result is obtained for different charge injection mechanisms including Schottky, Pool-Frenkel, and tunneling scenarios. Thus, it is shown that a single imprint mechanism can be responsible for a nolinear (in logarithmic scale) time dependence of the voltage offset and polarization loss. Additionally, the temperature dependence of the logarithmic rate of imprint is shown to be nonexponential. The developed model ties together the time and temperature dependences of imprint. For the experimental verification of the model a study of imprint has been performed on (111) filmcapacitors with temperatures ranging from 25 to and exposure times up to . It has been found that the theory developed adequately describes the obtained experimental data. Based upon the theoretical and experimental results a test for ferroelectric memories is proposed, which enables the long-term prediction of polarization loss caused by imprint for a wide temperature range and for different operating voltages.

The relaxor type of ferroelectric material , which has a partially disordered perovskite structure, has been characterized and shown a maximum plateau of the dielectric permittivity depending upon the temperature. The dielectric constant at a low frequency is up to 30 000 at room temperature. While the single-phase -doped , has a monoclinic structure solid solutions up to , the lattice parameters decrease with an increasing concentration. The temperature dependence of the dielectric constant of the -doped was measured with different contents, showing that the dielectric permittivity is higher than at an concentration. The present dielectric dispersion was interpreted on the basis of the interfacial polarization at the grain-boundary region.

Structural distortion of ferroelectric thin films caused by film strain has a strong impact on the microwave dielectric properties.thin films epitaxially grown on substrates using molecular beam epitaxy are extremely strained (i.e., in-plane tensional strain) from of bulk . The room-temperature in-plane dielectric constant and its tuning of the films at are observed to be 6000 and 75% with an electric field of , respectively. The control of strain in provides a basis for room-temperature tunable microwave applications by elevating its phase-transition peak to room temperature.

Piezoelectric actuators normally have complicated structures and work under severe loading conditions, e.g., high driving electric field and significant compressive preload. This study is focused on the experimental investigation of the electromechanical properties of a commercial soft lead zirconate titanate material under loading conditions simulating the in-service environment of high-strain actuators. The polarization and strain responses were first measured under a constant-stress preload. A significant enhancement of the dielectric and piezoelectric performance is observed within a small prestress range. At much higher preload levels, the predominant mechanical depolarization effect makes the material exhibits hardly any piezoeffect. In the other two series of tests, the specimen was subjected to cyclic mechanical load with different mean stresses and amplitudes. When the stress is applied in-phase with electrical loading, the polarization and strain outputs are found to monotonically decrease with an increase in stress amplitude, until mechanical loading completely impedes the piezoelectric response. An inverse effect occurs for the out-of-phase electromechanical loading tests, in which the polarization and strain outputs increase with increasing stress amplitude. In general, the enhanced polarization and strain responses are accompanied by an unfavorable increased hysteresis and, consequently, increased energy loss. An attempt has been made to explain the experimental findings by simultaneously taking into account the effects of dielectric response, elastic deformation, irreversible domain switching, and piezoeffects.

Grazing incidence x-ray reflectivity measurements are used to determine the density of sputter-deposited and anodized films. Together with refractive index and dielectric constant measurements, it is demonstrated that a coherent picture emerges explaining the low dielectric constant of the amorphous films as compared to the single-crystal value . The importance of molecular volume dependence of the electronic and vibrational molecular polarizabilities is underlined.

An analytical bilayer model has been developed to consider the effect of the existence of a dead layer (e.g., due to polarization degradation) at the film-electrode interface in an otherwise homogeneous ferroelectric thin film. By introducing asymmetric conductivity in the dead layer, the anomalous horizontal (along the field axis) shift behavior of hysteresis loops in ferroelectric thin films is successfully reproduced. Assuming that the ferroelectrichysteresis loops of the layers are parallelogramlike, explicit expressions are derived for calculating the internal fields in the film, as well as the “apparent” loop as measured from a Sawyer-Tower circuit. The general switching sequence for the ferroelectric phases will be considered. Using the ferroelectric-ferroelectric bilayer model, other anomalous phenomena, including vertical shift and deformed loop shape are also modeled.